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Performance enhancement of photovoltaic modules by nanofluid cooling: A comprehensive review
摘要： Only 15-20% of solar radiation incident on the photovoltaic (PV) cells is utilized which further reduces due to the rise in the temperature of the PV module and it also degrades the lifespan of the PV module. Therefore, numerous attempts were made to reduce this rising temperature of the PV module and different cooling techniques were employed. Nanofluid cooling is one of the potential cooling techniques for lowering the temperature of the PV module and augmenting the heat transfer by increasing the thermal conductivity of the nanofluid relative to the base fluid (BF). The experimental and numerical studies related to the cooling of PV cells with nanofluids have been reviewed. It was found that the heat transfer from the back of the PV module is enhanced with the augmentation in the concentration of nanoparticle in BF; however, some studies also demonstrate that the enhancement in the heat transfer also depends upon other factors such as the geometry at the rear of the PV module, nanoparticle material, nanoparticle size, BF, ambient conditions, etc. This review article also demonstrates the various issues with nanofluids such as instability, technological difficulties, high system costs, and the impossibility of finding a viable operational design which creates a barrier in the commercialization of the nanofluid cooling technique for PV modules.
关键词： photo-electric conversion efficiency,PV module cooling,photovoltaic cells,nanofluid cooling
更新于2025-09-16 10:30:52
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Exergoeconomic analysis of a solar photovoltaic-based direct evaporative air-cooling system
摘要： The target of this work is to perform the exergoeconomic analysis of a solar photovoltaic-based direct evaporative air-cooling system. The system was investigated experimentally with different thicknesses of cellulose and straw pads. For inlet air rates up to 1000 m3/h, the maximum changes in the humidity and temperature of outlet air are achieved by a pad with a thickness of 30 cm. A comprehensive mathematical model was developed for the system and the exergoeconomic analysis of the system was carried out. The influence of the effective parameter on the performance of the system was investigated. For an inlet air with a temperature of 30 °C and relative humidity of 30%, the maximum system exergy efficiency was obtained about 20%. With changes in the water temperature from 15 to 27 °C, inlet air rate from 300 to 1500 m3/h, and inlet air temperature from 26 to 34 °C, the system exergoeconomic factor changes up to 60%. The current system was compared with a conventional system and results showed that for four early years of systems lifetime, the exergoeconomic factor of the conventional system is greater than the solar system due to its lower initial investment, and for later years is lower due to its larger operating cost.
关键词： Cellulose and straw pads,Mathematical modeling,Exergoeconomic analysis,Solar photovoltaic panel,Direct evaporative air-cooling
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Las Vegas, NV, USA (2019.5.28-2019.5.31)] 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Additive Laser Metal Deposition Onto Silicon for Enhanced Microelectronics Cooling
摘要： We previously demonstrated how the Sn3Ag4Ti alloy can robustly bond onto silicon via selective laser melting (SLM). By employing this technology, thermal management devices (e.g., micro-channels, vapor chamber evaporators, heat pipes) can be directly printed onto the electronic package (silicon die) without using thermal interface materials. Under immersion two-phase cooling (pool boiling), we compare the performance of three chip cooling methods (conventional heat sink, bare silicon die and additively manufactured metal micro-fins) under high heat flux conditions (100 W/cm2). Heat transfer simulations show a significant reduction in the chip temperature for the silicon micro-fins. Reduction of the chip operating temperature or increase in clock speed are some of the advantages of this technology, which results from the elimination of thermal interface materials in the electronic package. Performance and reliability aspects of this technology are discussed through experiments and computational models.
关键词： Performance and Reliability,Thermal Management,Laser Metal Deposition,Additive Manufacturing,Electronic Cooling
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Intraband Ultrafast Terahertz Conductivity Dynamics in Graphene
摘要： The cooling mechanism is crucial for nanoelectronics, which determines the response time limited for the devices. The cooling process after optical pump in graphene, which is a well-known material with ultrahigh carrier mobility, is therefore an urgent research topic. Ultrafast thermalization and relaxation process in a monolayer graphene film grown on a quartz substrate is investigated by femtosecond laser pump, terahertz probe induced negative technique. A typical photo found, and the electron-phonon-impurity supercollision process is determined to about 2.8 picosecond at different pump photon energy and pump fluence. The competition between the impurity supercollision and the interband-intraband scattering in graphene could give new insight into the design of the application of graphene photonic devices.
关键词： ultrafast dynamics,cooling mechanism,electron-phonon-impurity supercollision,terahertz conductivity,graphene
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Regime of Multi-Stage Trapping in Free Electron Lasers
摘要： Novel schemes of a trapping regime in FELs were studied. Proof-of-principle experiments on realization of “non-resonant” trapping were performed at Ka-band. For short-wavelength FELs we describe two different ways of the use of regime of “multi-stage” trapping. First, this regime can be a way for efficiency enhancement of FELs operating in SASE regime. Second, multi-stage amplification of a single-frequency RF signal can lead to an effective cooling of the operating electron beam.
关键词： electron beam cooling,multi-stage trapping,efficiency enhancement,non-resonant trapping,FELs
更新于2025-09-16 10:30:52
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Effect of Interlayer Cooling Time, Constraint and Tool Path Strategy on Deformation of Large Components Made by Laser Metal Deposition with Wire
摘要： Laser metal deposition with wire (LMD-w) is a developing additive manufacturing (AM) technology that has a high deposition material rate and efficiency and is suitable for fabrication of large aerospace components. However, control of material properties, geometry, and residual stresses is needed before LMD-w technology can be widely adopted for the construction of critical structural components. In this study, we investigated the effect of interlayer cooling time, clamp constraints, and tool path strategy on part distortion and residual stresses in large-scale laser additive manufactured Ti-6Al-4V components using finite element method (FEM). The simulations were validated with the temperature and the distortion measurements obtained from a real LMD-w process. We found that a shorter interlayer cooling time, full clamping constraints on the build plates, and a bidirectional tool path with 180° rotation minimized part distortion and residual stresses and resulted in symmetric stress distribution.
关键词： Ti-6Al-4V,part deformation,process parameter optimization,interlayer cooling time,large-scale additive manufacturing
更新于2025-09-16 10:30:52
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Comparison of Electric Power Output Observed and Estimated from Floating Photovoltaic Systems: A Case Study on the Hapcheon Dam, Korea
摘要： An interest in floating photovoltaic (PV) is growing drastically worldwide. To evaluate the feasibility of floating PV projects, an accurate estimation of electric power output (EPO) is a crucial first step. This study estimates the EPO of a floating PV system and compares it with the actual EPO observed at the Hapcheon Dam, Korea. Typical meteorological year data and system design parameters were entered into System Advisor Model (SAM) software to estimate the hourly and monthly EPOs. The monthly estimated EPOs were lower than the monthly observed EPOs. This result is ascribed to the cooling effect of the water environment on the floating PV module, which makes the floating PV efficiency higher than overland PV efficiency. Unfortunately, most commercial PV software, including the SAM, was unable to consider this effect in estimating EPO. The error results showed it was possible to estimate the monthly EPOs with an error of less than 15% (simply by simulation) and 9% (when considering the cooling effect: 110% of the estimated monthly EPOs). This indicates that the approach of using empirical results can provide more reliable estimation of EPO in the feasibility assessment stage of floating PV projects. Furthermore, it is necessary to develop simulation software dedicated to the floating PV system.
关键词： Hapcheon Dam,PV system,natural cooling effect,Floating PV,electric power output
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Zn:MgO:PPLN Waveguides for Rb Cold Atom Trap Based Quantum Gravitometry in a CubeSat
摘要： Satellite based experiments require laser systems that are compact and efficient, which are robust against vibration, radiation and thermal cycling. Supported by Innovate UK’s Quantum Technology ‘Cold Atom Space PAyload (CASPA)’ project we have fabricated PPLN (Periodically Poled Lithium Niobate) ridge waveguides to act as efficient frequency converters for rubidium atom cooling via second harmonic generation (SHG) of telecoms lasers. CASPA is a technology demonstrator for magneto-optical cooling within a micro CubeSat laying the foundations for novel gravitometry and global positioning techniques. With respect to the particular environment of operation we have developed single mode ridge waveguides with metal indiffusion and dicing. We fabricate PPLN ridge waveguides by firstly high-voltage poling of z-cut magnesium doped lithium niobate, then deposit and thermally indiffuse Zn to create planar optical confinement, followed by ultra-precision ductile dicing to define ridge waveguides and coupling facets. Our non-AR coated waveguides have produced optical to optical efficiencies of up to 22.0 %, producing 44.7 mW of SHG with 203 mW of transmitted pump. The 2nd moment MFD was calculated to be 10.8 and 10.0 μm in the x and y axes, respectively, allowing efficient mode matching to standard telecommunication fibre. With a free space launch we have measured an average insertion loss, over multiple dies, of -1.3 dB, for 4 cm long waveguides that are non-AR coated. When comparing to other ridge PPLN waveguides this is a 3.7 dB improvement over competing examples of a 5 cm bonded and thinned device and a 1.9 dB improvement for a 1 cm proton exchange device. These low insertion losses can be attributed to both the symmetric pump mode of the waveguides enabling efficient mode matching and low amounts of optical scattering from waveguide sidewall roughness. We have shown ductile dicing to produce an average surface roughness of 0.29 nm (Sa) on waveguide facets in a single processing step.
关键词： CubeSat,rubidium atom cooling,second harmonic generation,ridge waveguides,PPLN
更新于2025-09-16 10:30:52
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Recent Developments in Efficiency Enhancement of Non-Concentrating Photovoltaic Systems by Thermal Methods
摘要： Two different methods for reducing the operating temperatures of non-concentrating photovoltaic panels are analyzed and the performances are compared. Forced air cooling using a low power fan and use of a thermo siphon heat pipe are the modifications proposed for the purpose of efficiency enhancement. Experimental results of the two techniques are compared. It was found that, using a specific flow rate and selection of the proper heat pipe fluid and its operating conditions could help to reduce panel temperature considerably.
关键词： Temperature effects,Panel cooling,Photovoltaic,Efficiency enhancement
更新于2025-09-16 10:30:52
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Acousto-optic modulators for a controlled frequency shift of light beams in optical and microwave cold-atom frequency standards
摘要： A series of specialised acousto-optic modulators/frequency shifters based on paratellurite (TeO2) single crystals is developed for systems of laser cooling and frequency stabilisation of laser sources in optical and microwave frequency standards based on cold strontium, rubidium and caesium atoms. The methods of calculation and optimisation of the main parameters of acousto-optic modulators are considered; their basic technical characteristics are experimentally investigated in the spectral range of optical radiation 460 – 900 nm and in the frequency shift range of 5 – 400 MHz. The modulators have a high diffraction efficiency, low power consumption and the ability to work with linearly and randomly polarised optical radiation.
关键词： frequency shifter,modulator,acousto-optic diffraction,frequency stabilisation,laser cooling,frequency shift,frequency standards
更新于2025-09-16 10:30:52